This is likely a result of the problem noted here
Having that many kernels kept is definitely more than the expected amount.
What is the result of df -h ? (so we can see the actual size of /boot and how much is used)
Reducing the number of kernels to keep was a good thing.
Manually removing kernel files is not so good and idea. There are a lot of files located in other locations and proper removal requires removing the packages that installed them.
To remove an older kernel manually (which includes the files in /boot) is easily done with dnf
sudo dnf remove kernel\*<version-number>\*
This will remove all the kernel files related to that version of the kernel as well as any dependencies.
The entry protected_packages=kernel-6.17.5-300.fc43.x86_64 in the file you edited is not necessary and may cause issues in the future. I assume you meant that is the entry in /etc/dnf/dnf.conf.